Field of the Invention
The present invention relates to the diagnosis or the prognosis of metastasis, in particular bone metastasis, in lung cancer based on determining if the c-MAF gene is amplified in a primary tumor sample. Likewise, the invention also relates to a method for the diagnosis or the prognosis of metastasis in lung cancer, in particular bone metastasis, as well as to a method for designing a customized therapy in a subject with lung cancer, which comprises determining the c-MAF gene expression level. Finally, the invention relates to the use of a c-MAF inhibitor as therapeutic target for the treatment of lung cancer metastasis, in particular bone metastasis.
Background Art
Metastasis, a complex process caused by elaborate interactions between tumor cells and the surrounding normal tissues in different vital organs, accounts for 90 percent of all cancer deaths in patients with solid tumors. The molecular and cellular mechanisms that lead primary tumors to form metastases must be understood in order to better address this major life-threatening problem. The identification of metastasis genes and mechanisms is essential for understanding the basic biology of this lethal condition and its implications for clinical practice. Previous work provided a sense of the complexity of the metastasis process, but it failed to explain how and why metastasis occurs, what mechanisms make metastasis a tissue-specific process, what events allow dormant metastases to become active and lethal many years after removal of a primary tumor, and what metastasis-mediating genes would eventually constitute worthy diagnostic markers and therapeutic targets.
Lung Bone-Specific Metastasis
Lung cancer is a disease characterized by uncontrolled cell growth in tissues of the lung. If left untreated, this growth can spread beyond the lung in a process called metastasis into nearby tissue and, eventually, into other parts of the body. Most cancers that start in lung, known as primary lung cancers, are carcinomas that derive from epithelial cells. Worldwide, lung cancer is the most common cause of cancer-related death in men and women, and is responsible for 1.3 million deaths annually, as of 2004. The most common symptoms are shortness of breath, coughing (including coughing up blood), and weight loss.
Lung cancers consist of four major types of lung cancer and multiple minor or rare forms. For clinico-pathological reasons they are often divided into the broad categories of small-cell lung cancer (SCLC), also called oat cell cancer, and non-small-cell lung cancer (NSCLC). NSCLC is further divided into three major types, squamous cell carcinoma (SCC), adenocarcinoma and large cell carcinomas. Because large cell carcinomas might represent poorly or undifferentiated forms of the other types of cancers, it is a vaguely defined entity, and criteria for its diagnosis vary widely. The most common cause of lung cancer is long-term exposure to tobacco smoke. Nonsmokers account for 15% of lung cancer cases, and these cases are often attributed to a combination of genetic factors, radon gas, asbestos, and air pollution including secondhand smoke.
Similar to many other cancers, lung cancer is initiated by activation of oncogenes or inactivation of tumor suppressor genes. Oncogenes are genes that are believed to make people more susceptible to cancer. Proto-oncogenes are believed to turn into oncogenes when exposed to particular carcinogens. Mutations in the K-ras proto-oncogene are responsible for 10-30% of lung adenocarcinomas. The epidermal growth factor receptor (EGFR) regulates cell proliferation, apoptosis, angiogenesis, and tumor invasion. Mutations and amplification of EGFR are common in non-small-cell lung cancer and provide the basis for treatment with EGFR-inhibitors. Her2/neu is affected less frequently. Chromosomal damage can lead to loss of heterozygosity. This can cause inactivation of tumor suppressor genes. Damage to chromosomes 3p, 5q, 13q, and 17p are particularly common in small-cell lung carcinoma. The p53 tumor suppressor gene, located on chromosome 17p, is affected in 60-75% of cases. Other genes that are often mutated or amplified are c-MET, NKX2-1, LKB1, PIK3CA, and BRAF.
Several genetic polymorphisms are associated with lung cancer. These include polymorphisms in genes coding for interleukin-1, cytochrome P450, apoptosis promoters such as caspase-8, and DNA repair molecules such as XRCC1. People with these polymorphisms are more likely to develop lung cancer after exposure to carcinogens.
Classification
Lung cancers are classified according to histological type. This classification has important implications for clinical management and prognosis of the disease. The vast majority of lung cancers are carcinomas—malignancies that arise from epithelial cells. The two most prevalent histological types of lung carcinoma, categorized by the size and appearance of the malignant cells seen by a histopathologist under a microscope, are non-small-cell and small-cell lung carcinoma. The non-small-cell type is the most prevalent by far.
Cancer found outside of the lung may be determined to have arisen within the lung, as lung cancers that metastasize, i.e. spread, often retain a cell marker profile that allow a pathologist to say, with a good deal of certainty, that the tumor arose from the lung, i.e. is a primary lung cancer. Primary lung cancers of adenocarcinoma histology typically have nuclear immunostaining with TTF-1.
Non-Small-Cell Lung Carcinoma
The non-small-cell lung carcinomas (NSCLC) are grouped together because their prognosis and management are similar. There are three main sub-types: squamous cell lung carcinoma, adenocarcinoma, and large-cell lung carcinoma.
Accounting for 25% of lung cancers, squamous cell lung carcinoma usually starts near a central bronchus. A hollow cavity and associated necrosis are commonly found at the center of the tumor. Well-differentiated squamous cell lung cancers often grow more slowly than other cancer types.
Adenocarcinoma accounts for 40% of non-small-cell lung cancers. It usually originates in peripheral lung tissue. Most cases of adenocarcinoma are associated with smoking; however, among people who have never smoked (“never-smokers”), adenocarcinoma is the most common form of lung cancer. A subtype of adenocarcinoma, the bronchioloalveolar carcinoma, is more common in female never-smokers, and may have different responses to treatment.
Small-Cell Lung Carcinoma
Small-cell lung carcinoma (SCLC) is less common. It was formerly referred to as “oat-cell” carcinoma. Most cases arise in the larger airways (primary and secondary bronchi) and grow rapidly, becoming quite large. The small cells contain dense neurosecretory granules (vesicles containing neuroendocrinehormones), which give this tumor an endocrine/paraneoplastic syndrome association. While initially more sensitive to chemotherapy and radiation, it is often metastatic at presentation, and ultimately carries a worse prognosis. Small-cell lung cancers have long been dichotomously staged into limited and extensive stage disease. This type of lung cancer is strongly associated with smoking.
Prognosis
Prognostic factors in non-small-cell lung cancer include presence or absence of pulmonary symptoms, tumor size, cell type (histology), degree of spread (stage) and metastases to multiple lymph nodes, and vascular invasion. For patients with inoperable disease, prognosis is adversely affected by poor performance status and weight loss of more than 10%. Prognostic factors in small-cell lung cancer include performance status, gender, stage of disease, and involvement of the central nervous system or liver at the time of diagnosis.
For non-small-cell lung carcinoma (NSCLC), prognosis is generally poor. Following complete surgical resection of stage IA disease, five-year survival is 67%. With stage IB disease, five-year survival is 57%. The five-year survival rate of patients with stage IV NSCLC is about 1%.
For small-cell lung carcinoma, prognosis is also generally poor. The overall five-year survival for patients with SCLC is about 5%. Patients with extensive-stage SCLC have an average five-year survival rate of less than 1%. The median survival time for limited-stage disease is 20 months, with a five-year survival rate of 20%.
According to data provided by the National Cancer Institute, the median age at diagnosis of lung cancer in the United States is 70 years, and the median age at death is 72 years. In the US, people with medical insurance are more likely to have a better outcome.
Metastasis
Primary lung cancers themselves most commonly metastasize to the adrenal glands, liver, brain, and bone.
Skeletal metastasis occurs in advanced-stage lung cancer and they confer a high level of morbidity. At first diagnosis of bone metastasis disease therapeutic intervention will usually involve systemic chemotherapy, radiotherapy and bisphophonates, which are mostly palliative options with the intention of reducing pain.
In healthy skeletal bone, an equal balance of new bone matrix formation and old bone matrix resorption is achieved via coordinated activity of bone-degrading osteoclasts and bone-forming osteoblasts. During metastasis bone disease, the normal balance of bone resorption and formation is disrupted by the homotypic and heterotypic cell-cell interactions that occur between invading tumor cells, osteoblasts and ostoclasts. Most patients with secondary bone tumors—including those associated with lung cancer present with osteolytic lesions. Therefore, most treatment strategies in current use or under evaluation in metastasis bone disease have been designed to protect the bone matrix from increased bone degrading activity of osteoclasts. Bone metastasis osteolytic lesions of the lung are a common feature with those of the breast, as opposed to prostate cancer. In the latter, an additional complication present in castration-resistant prostate cancer and metastasis bone disease are osteosclerotic lesions—also known as bone-forming or osteoblastic lesions- or a combination of both, osteolytic and osteosclerotic lesions—also referred to as mixed lesions. Osteosclerotic lesions are typified by bone deposits with multiple layers of poorly organized type-I collagen fibrils that have a woven appearance and reduced mechanical strength. Based on the common phenotypic features of lung and breast cancer bone metastasis is likely that the process underlines similar molecular mechanisms.
Lung cancer cells preserve, among each subtype, genome-aberration-induced transcriptional changes with high fidelity. The resulting dominant genes will reveal molecular events that predict the metastatic outcome despite the existence of substantial genomic, transcriptional, translational, and biological heterogeneity in the overall system. However, it is unknown whether the developmental history of a cancer would result in different or common mediators of site-specific metastasis. Predisposing factors related to the cell of origin may engender different rate-limiting barriers during metastatic progression. The present patent aims to set the stage for a detailed new prognostic factor to predict metastasis to the bone and their potential value as a therapeutic target.
The fact that most of the patients with solid tumor cancer die after metastasis means that it is crucial to understand the molecular and cellular mechanisms allowing a tumor to metastasize. Recent publications have demonstrated how the metastasis is caused by means of complex yet little known mechanisms and also how the different metastatic cell types have a tropism towards specific organs. These tissue specific metastatic cells have a series of acquired functions allowing them to colonize specific organs.
However, there are no genetic markers, in the state of the art, which allow the diagnosis and/or the prognosis of whether a patient who suffers a specific lung cancer, such as NSCLC lung cancer, will or will not suffer metastasis, thus a suitable therapy being able to be applied to the subject suffering said cancer. Therefore, there is the need of identifying new markers which allow diagnosing the presence of metastasis in subjects suffering lung cancer and/or predicting the probability of a subject suffering lung cancer to develop metastasis, in particular bone metastasis. The identification of new prognosis factors will serve as a guide in selecting the most suitable treatments.
Identification of markers that predict bone metastasis would provide a preventive therapeutic opportunity by imposing restrictions to the spreading and colonization of bone metastatic tissue by lung cells and delay or transform a lethal condition. The inventors identified c-MAF and 16q22-24 genomic gain, as a bona fide associated lung cancer bone metastasis gene and genomic alteration, in a preferred embodiment osteolytic prostate bone metastasis.